1. Field
The present disclosure relates to a wave antenna system. In particular, a wave antenna lens system comprising a double-ended array of wave antennas deployed in a lens shape is disclosed.
The system disclosed in the present application can be applied to a wide range of microwave and millimeter wave antennas, where quasi-optical elements, i.e. elements having properties resembling those of optical elements, can improve performance, for example by focusing radiation in antenna systems. In particular, the lens system disclosed in the present application can be used to replace a fixed reflector or a lens, for example in satellite tracking applications.
2. Description of related art
There are a number of mechanisms that are classically used to focus radiation in antenna systems:
a) Mirrors and focal plane sensors, where a lens or a reflecting metal surface can be used to focus radiation. Typical satellite antennas are provided with a detector at the focus of an offset parabolic reflector, like for example in DirecTV or DirecPC applications. The parabola is offset for reasons related to beam blockage and diffraction by the supports.
b) Lens systems. However, these kinds of systems are less used in the microwave bands because of the dimensions, performance (reflective losses) and costs of the lenses when compared with those of a metal mirror. In fact, while optical lenses can have anti-reflecting coatings, these coatings are often not suited to coherent microwaves.
c) Thin lenses making use of Fresnel designs, such as used in the optical domain. However, for longer wavelengths, the step size must correspond to integer wavelengths, in order to avoid strong grating lobes due to diffraction at these locations. The grating lobe problem limits the utility of the lens for tracking.
d) Transmitting Fresnel zone plates. Again, there are beam steering issues that make this difficult.
e) Rotman-Turner lens, where a pair of one- or two-dimensional arrays of horns are connected together via waveguide links. Each link has a fixed phase delay designed to produce a phase shift equivalent to that of a lens. However, horns and metallic guides are needed.